<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>计算圆的面积和周长</title>
</head>
<body>
    <script>
        var r = prompt('请输入圆的半径');
        r = parseFloat(r);
        var c = 2*3.14*r;
        var s = 3.14*r*r;
        //在控制台输出圆的周长和面积
        console.log('圆的周长为：'+c.toFixed(2));
        console.log('圆的面积为：'+s.toFixed(2));
    </script>
</body>
</html>